Method for separating thiophene from benzene



U i ed St s Pm METHOD FOR SEPARATING THIOPHENE FROM BENZENE Albert W. Simon, McKeesport, Pa., assignor to United States Steel Corporation, a corporation of New Jersey No Drawing. Application October 9, 1957 Serial N0. 639,048

2 Claims. (Cl. 208240) This invention relates to the purification of cokeoven light-oil fractions such as benzene and, in particular, to a method for separating thiophene therefrom.

The standards of purity set by consumers of benzene are being raised progressively. Thiophene is one of the most troublesome impurities found in benzene because its properties are so similar to those of benzene that separation is diflicult and expensive. Washing with concentrated sulfuric acid or treatment with aluminum chloride is common practice but there are serious objections to both these reagents. Accordingly, the object of my invention is to provide a simple, inexpensive method for separating thiophene from benzene.

I have found that, when benzene is distilled in the presence of a small amount of diphenylsulfone or dihydroxydiphenyl sulfone, there is a marked reduction in the thiophene content of the benzene. The distillation may be effected by conventional methods and apparatus. The

amount of diphenylsulfone or dihydroxydiphenylsulfone added may be from 0.1 to 10.0% by weight of the benzene, preferably about 3%. The details of the invention will be apparent from the following explanation of typical examples thereof.

EXAMPLE 1 Ten grams of diphenylsulfone Was added to 350 ml. of benzene that contained 7.4 p.p.m. of thiophene. The resulting mixture Was subjected to a distillation through a four-foot packed column, the benzene being taken overhead as distillate. The thiophene analyses of the fractions collected are given in Table I. Also included in the table are the results from a control test on another sample of the same starting benzene in which all the conditions were held the same except that no diphenylsulfone was added.

These results show that the presence of diphenylsulfone resulted in a distillate with an average thiophene content of 0.95 p.p.m., while the distillation in which no diphenylsulfone was used gave a distillate containing 3.4 p.p.m. of thiophene. The use of diphenylsulfone thus achieved a reduction in thiophene content of 87% while phene content only 54%.

' EXAMPLE 2 Ten grams of diphenylsulfone was added to 350 ml. benzenewhich contained 508 p.p.m. of thiophene and the. mixture was distilled as before. After the distillation, the distillate was analyzed for thiophene. The results are given in Table II. Also included in the table are the results from a control test on another sample of the same starting benzene in which all of the conditions were held the same except that no diphenylsulfone was added. The data indicate that the diphenylsulfone is responsible for a reduction of the thiophene content of 76% while distillation without diphenylsulfone reduced the thiophene content only 40%.

Table II Thiophene Content, p.p.m. Volume, Fraction Number ml.

With Diphenyl- With No sulfone Sulfone 1 Total. 1 Average.

EXAMPLE 3 Ten grams of dihydroxydiphenylsulfone (a commercial mixture containing mainly 4,4-dihydroxydiphenylsulfone and some 2,4-dihyroxydiphenylsulfone) was added to 350 ml. of benzene containing 508 p.p.m. of

thiophene and the mixture distilled as before. The results of the distillation are given in Table III.

Table III Thiophene Content, D-De Volume, Fraction Number ml.

With Dihydroxy- With No diphenyl- Sulfone sulfone 1 Total. 9 Average.

The distillation from dihydroxydiphenylsulfone gave a distillate containing 108 p.p.m. of thiophene, a reduction of 79%. The benzene from a control distillation in which no sulfone was present contained 306 p.p.m. of thiophene, a reduction fo 40%.

It will be apparent that the presence of the additive greatly enhances the thiophene removal eifected by distillation. A minimum of about 0.1% of the additive is necessary to give improved removal of thiophene. A greater amount may be employed but over 10% does not give any gain in thiophene removal. Diphenylsulfone is a cheap noncorrosive compound, easily made by reacting sulfur trioxide or fuming sulfuric acid with benzene. Dihydroxydiphenylsulfone can be made from phenol in Patented Feb. 23, 12x50.

a similar manner. Because of their high boiling points, the sulfones remain in the distillation pot. After a distillation has been completed, the thiophene concentrate may be flashed off and the sulfone recycled for further use.

The invention is also applicable to the removal of out departing from the spirit and scope of the invention.

I claim: 1. The method of separating thiophene from cokeoven light-oil fractions which comprises adding to such fractions from 0.1% to 10% by weight, of'a reagent selected from the group consisting of diphenylsulfone and dihydroxydiphenylsulfone, and distilling the resuling mixture.

2. The method of separating thiophene from coke-oven light-oil fratcions which comprises adding to such fractions about 3% by weight, of a reagent selected from the group consisting of diphenylsulfone and dihydroxydiphenylsulfone, and distilling the resulting mixture.

References Cited in the file of this patent UNITED STATES PATENTS 2,427,988 Wilson et al. Sept. 23, 1947 OTHER REFERENCES Chemical Abstracts, vol. 19, page 2557 (1925). 

1. THE METHOD OF SEPARATING THIOPHENE FROM COKEOVEN LIGHT-OIL FRACTIONS WHICH COMPRISES ADDING TO SUCH FRACTIONS FROM 0.1% TO 1/% BY WEIGHT, OF A REAGENT SELECTED FROM THE GROUP CONSISTING OF DIUPHENYLSULFONE AND DIHYDROXYDIPHENYLSULFONE, AND DISTILLING THE RESULING MIXTURE. 